An infusion pump is used to infuse fluids, medication or nutrients into a patient's circulatory system. It is generally used intravenously, although subcutaneous, arterial and epidural infusions are occasionally used.
Infusion pumps can administer fluids in ways that would be impractically expensive or unreliable if performed manually. For example, infusion pumps can administer 1 mL per hour injections (too small for a drip), injections every minute, injections with repeated boluses requested by the patient, up to the maximum number per hour allowed (e.g. in patient-controlled analgesia), or fluids whose volumes vary by the time of day.
As infusion pumps can also produce quite high but controlled pressures, the pumps can inject controlled amounts of fluids subcutaneously (beneath the skin), or epidurally (just within the surface of the central nervous system—a very popular local spinal anesthesia for childbirth).